Portrait of a physicist explores our need to know

CAMBRIDGE - The new Central Square Theater certainly knows its neighborhood. The handsome black-box theater, a joint project of the Nora Theatre Company and Underground Railway Theater, opened its doors this weekend with a lively blend of music and math, drama and science, art and life. You can't get much more Cambridge than that.

In repertory with a reprise of jazzman Stan Strickland's luminous "Coming Up for Air" - an unforgettable autobiographical show, written and directed by Jon Lipsky, that debuted in Boston in 2006 - the theater is presenting "QED," Peter Parnell's play about the eccentric, brilliant physicist Richard Feynman (also directed, beautifully, by Lipsky). It's an apt pairing, and not just because Feynman had his musical side as well as his mathematical one.

Both shows weave personal anecdotes and musings into something larger and more universal. Both touch on fear, loss, and death, and both leave us with a richer, more expansive sense of what it means to be alive. And "QED," like "Coming Up for Air," paints a vivid portrait of a fascinating person - it's just that, in this case, the person is not a beloved local musician but an award-winning California Institute of Technology professor and Nobel laureate (the play's title comes from the work that brought him that honor, on quantum electrodynamics) who died in 1988.

"QED" also fits neatly into the mission of the Catalyst Collaborative @ MIT, which Underground Railway and MIT founded as a way of building links between theater and science. Sunday afternoon's audience seemed more scientific than your typical theater crowd - there were knowing chuckles at a few references that went right over this liberal-arts major's head - but the play is truly a play, not a physics lecture. Like Feynman does, it humanizes scientific questions, and it makes them seem accessible without ever talking down to its audience.

Parnell originally wrote the play for Alan Alda, who performed it in 2001. Keith Jochim, who plays Feynman here, is less angular, more solidly built, than Alda, but he has a similar buoyant energy and unforced charm. "QED" is billed as "an evening with Richard Feynman," and that's just what it feels like with Jochim effortlessly holding our attention onstage: two hours in the company of a great raconteur with a sharp mind, an endless curiosity, and an infectious enthusiasm for life.

The play is almost a one-man show, but Danielle Kellerman shows up periodically as an inquisitive student. Kellerman fills that part nicely, both in her first, slightly dowdy incarnation and in a later visit (after the cast party for a student production of "South Pacific," in which Feynman has just played the chief of Bali Hai) that finds her in considerably looser spirits. But the role itself feels dramatically unnecessary; it allows the playwright to weave in a bit more exposition, but it doesn't really add to our understanding of the only character we're really interested in here, Feynman himself.

Even so, the play's structure is generally deft, with few of the awkward contrivances that can make the mechanics of telling a life story onstage feel too obvious. Parnell simply gives us Feynman, in his office on a Saturday, working on a lecture he'd forgotten to prepare, taking phone calls, playing his drum, and looking back at his life.

The title of the lecture he's been asked to give is "What We Know." Feynman scoffs at the ridiculousness of that ambitious aim - then proceeds, over the course of this marvelously humane show, to give us a pretty good tour of exactly that.